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chat: fix int overflow, prevent size calculation in float/double #17357

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Merged
ngxson merged 2 commits into from
Nov 18, 2025
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chat: fix int overflow, prevent size calculation in float/double #17357

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b33603e
chat: fix int overflow, prevent size calculation in float/double
ngxson Nov 18, 2025
6d3d572
Update common/chat.cpp
ngxson Nov 18, 2025
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10 changes: 8 additions & 2 deletions common/chat.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3009,7 +3009,7 @@ static common_chat_params common_chat_templates_apply_legacy(
const struct common_chat_templates * tmpls,
const struct common_chat_templates_inputs & inputs)
{
int alloc_size = 0;
size_t alloc_size = 0;
std::vector<llama_chat_message> chat;
std::vector<std::string> contents;

Expand All @@ -3031,7 +3031,8 @@ static common_chat_params common_chat_templates_apply_legacy(
const auto & msg = inputs.messages[i];
const auto & content = contents[i];
chat.push_back({msg.role.c_str(), content.c_str()});
alloc_size += (msg.role.size() + content.size()) * 1.25;
size_t msg_sz = msg.role.size() + content.size();
alloc_size += msg_sz + (msg_sz / 4); // == msg_sz * 1.25 but avoiding float ops
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}

std::vector<char> buf(alloc_size);
Expand All @@ -3053,6 +3054,11 @@ static common_chat_params common_chat_templates_apply_legacy(
res = llama_chat_apply_template(src.c_str(), chat.data(), chat.size(), inputs.add_generation_prompt, buf.data(), buf.size());
}

// for safety, we check the result again
if (res < 0 || (size_t) res > buf.size()) {
throw std::runtime_error("failed to apply chat template, try using --jinja");
}

common_chat_params params;
params.prompt = std::string(buf.data(), res);
if (!inputs.json_schema.empty()) {
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